Electronic watch

ABSTRACT

A digital display for an electronic timepiece admitting of reduced power consumption by providing improved circuitry for driving same. The circuitry applies drive signals to each digit representative of a unit of time in a sequential manner so as to light each unit sequentially. The duty cycle is selected to render all of the display digits visible to the human eye simultaneously.

United States Patent Miura et al.

[451 July 15, 1975 [5 ELECTRONIC WATCH 3,760,584 9/1973 Dargent 58/50 R3,765,163 101973 L t'l. 58 50 R [751 Inventors: Teiii Himshi Takeshita,both 3 781,863 12/1973 F uji ia 58/50 R of Suwa, Japan [73] Asslgnee: rgg z ggp gs Suwa Selkosha Primary Examiner-Edith Simmons JackrnonAttorney, Agent, or FirmBlum, Moscovltz, Friedman [22] Filed: Dec. 18,1973 & Kaplan [21] App]. No.: 425,899

[30] Foreign Application Priority Data [57] ABSTRACT Dec. 18, 1972 Japan47-l27003 A digital display for an electronic timepiece admitting ofreduced power consumption by providing im- [52] US. Cl. 58/50 R; 235/92EA; 340/336 proved circuitry f i i Same The circuitry [51] Int. Cl. G04b19/30; H05b 39/09 plies drive Signals to each digit representative of aunit [58] Fleid of Search 58/50 R; 235/92 EA; of time i a Sequentialmanner so as to light each unit 340/324 sequentially. The duty cycle isselected to render all of the display digits visible to the human eyesimulta- [56] References Cited neous]y UNITED STATES PATENTS 3,707,07112/1972 Walton 58/50 R 5 Claims, 5 Drawing Figures I asc/tmmk DIV/DERCW/VTEI? /Z i I DECODER i I l 02/4/15 i H l C l I l r r r r I 7M/IV'6 ICO/VZ'POL r l 1 D/SPLA Y I I i D I I i i I I DA /t/E /3 ELECTRONIC WATCHBACKGROUND OF THE INVENTION In general, this invention is directed tosmall-sized electronic timepieces such as wrist watches, and inparticular to circuitry for driving a digital display in a small-sizedelectronic timepiece in a manner which produces minimal powerconsumption.

In small-sized electronic timepieces of the prior art, each of thedigital display elements representing units of time such as hours,minutes and seconds are driven simultaneously to thereby render sameviewable to the human eye. Because of the excessive amount of powerrequired to light such digital displays, it has been necessary to limitthe length of time that the digital display elements could remain lit.If the amount of time is not considerably limited, the increased powerconsumption caused by lighting the digital display elements will have amarked effect of the life of the battery used in the electronictimepiece, it being recognized that the capacity of such batteries isseriously limited in small sized electronic timepieces by obvious spacelimitations. Thus, it is necessary to provide a digital display which iseasily viewable yet provides minimum power consumption.

SUMMARY OF THE INVENTION Generally speaking, in accordance with theinvention, an electronic timepiece circuit is provided for driving adigital display in a manner which reduces the power consumption thereof.The electronic timekeeping circuit includes a high frequency signalgenerating oscillator, a multi-digit digital display, each digit adaptedto display a particular unit of time, and logic circuitry for receivingthe high frequency time standard signal from the oscillator andproviding same to drive circuits which are adapted to energize thedisplay elements. Within the logic circuit is a timing control circuitwhich causes the drive signals supplied by the drive circuits to thedisplay elements to be applied to each digit sequentially, the dutycycle being selected so as to render the display elements simultaneouslyvisible to a viewer.

When the display elements are formed from segmented digital displayelements, the timing control circuit is further adapted to providesequential energization of the segments as well, the duty cyclecombining with the after-image effect of the display elements to renderthe display elements simultaneously viewable by the viewer.

Accordingly, it is an object of this invention to provide an improvedsmall-sized electronic timepiece including a digital display whereinpower consumption is minimized.

It is a further object of the instant invention to provide an improvedsmall-sized electronic timepiece wherein hours, minutes and seconds arenot displayed simultaneously yet appear to be when viewed.

It is a further object of the instant invention to provide an improvedsmall-sized electronic timepiece wherein voltage drops caused by theinternal resistance of the digital display are eliminated.

It is still a further object of this invention to provide an improvedelectronic timepiece including a digital display wherein battery life isextended by the sequential energization of the digital display elements.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of theinvention, reference is had to the following description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a circuit diagram of an electronic timepiece including adigital display for providing minimal power consumption and constructedin accordance with the instant invention;

FIG. 2 is a wave diagram of signals applied to the display circuitdepicted in FIG. 1;

FIG. 3 is a circuit diagram of an electronic timepiece including adigital display constructed in accordance with still another embodimentof the instant invention;

FIG. 4 is a wave diagram of the pulses applied to the digital displaydepicted in FIG. 3; and

FIG. 5 is a wave diagram of the signals of still another embodiment, thesignals being applied to the digital display in accordance with theinstant invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, anelectronic time-keeping circuit in accordance with the invention isprovided, including a high-frequency signal generator A, the output ofwhich is applied to logic circuit B, the output of which is, in turn,applied to drive circuits C. Said drive circuits are coupled to adigital display D. The high frequency signal produced by the oscillatorof signal generator A is provided to a divider circuit 10 formed from achain of multi-stage dividers which produce a lower frequency signal;for example, a one-second signal for application to counter/decodercircuit 12, and an intermediate frequency signal for application totiming control circuit 11.

Timing control circuit 11 consists of a digital matrix which produces,from the signal applied thereto, eight sequential pulse signals to moreparticularly shown in FIG. 2, six of which are applied to the output oftiming control circuit 11, which output is applied to drive circuit l3and counter/decoder circuit 12.

Counter/decoder circuit 12 includes a further divider chain, whichproduces time-keeping signals representative of each digit of time on acontinuous basis from the signal received from divider circuit 10.Display D includes an hour, minute and seconds display having sixdigits, each of the digits formed of seven segments. The segmenteddisplay, generally known as a seven-bar display, is depicted, by way ofexample, in FIG. 3 of US. Pat. No. 3,756,011, which issued on Sept. 4,1973. The display elements defining each segment of each digit arepreferably formed of gallium arsenide phosphide light-emitting diodes inthe timepiece in accordance with the invention. In order to minimizepower consumption, each of the six digits of time is sequentiallyenergized for the duration of the associated pulse from timing controlcircuit 11 as shown in FIG. 2. The duty cycle for the output of timingcontrol circuit 11 is chosen so that one viewing the display would notnotice the flickering thereof due to retinal retention. A preferablepulse width is of the order of l/256th of a second. Thus, instead ofsimultaneously energizing all of the digits, the digits are sequentiallydisplayed at such speeds that it appears that all are lightedsimultaneously. Such a display sequence utilizes one-half or less of thepower that a digital display utilizes when all of the digits are lit atthe same time. The embodiment of FIG. 1 may take two forms. In a firstembodiment, like segments on each of the six digits would be connectedto a common drive circuit 14, which in turn could be connected torespective decoders or to a common decoder connected to respectivecounter circuits, the selection of the counter circuit coupled throughdrive circuit 14 to the digital display being controlled by the pulsesfrom timing control circuit 11 in coordination with the actuation of thedigits through drive circuit 13. This embodiment would save substantialcircuit elements, requiring only a single drive circuit 14, or ifdesired, a single decoder for converting the BCD output of therespective counters into a seven signal output suitable for driving theseven bar display. In such an embodiment, a logic circuit incorporatedin counter/decoder 12 would perform the selective connection of eitherthe counters or decoders, if more than one decoder is provided.

A second embodiment is depicted in FIG. 3 wherein like referencenumerals are applied to like elements. In this embodiment, each of thesegments of each of the digits are sequentially actuated. Thus, not onlyare each of the digits sequentially actuated, but each of the segmentswithin each of the digits are sequentially actuated. A low frequencyoutput of divider 10, for example a l-second signal, is applied tocounter/decoder 12' while intermediate frequency outputs are applied totiming control circuit 11'. Said timing control circuit generates sevenkinds of segment codes, corresponding to each segment of each digit, andsix kinds of digit codes, corresponding to each separate digit.Counter/decoder circuit 12' produces timing signals representative ofeach digit of time in a chain of counters. As discussed above inconnection with FIG. 1, these timekeeping signals can be applied toeither a common decoder or to separate decoders associated with eachdigit of time, the output ofthe common decoder or separate decodersbeing applied to a drive circuit 14.

The output signals from timing control circuit 11 opcrate through alogic circuit in counter/decoder circuit 12' so that each segment ofeach digit is sequentially actuated. This effect is achieved byassigning a time slot in the duty cycle to each segment of each digit.The signal applied in each time slot can come from either a common drivecircuit 14' or decoder, in which case logic circuitry in counter/decodercircuit 12 would selectively apply the output of the respective countercircuits of the counter chain to the common drive circuit 14, or throughseparate decoder and drive circuits for each digit, in which case theoutput of the respective drive circuit would be energized by the signalsfrom timing control 11' through a suitable logic circuit.

Similarly, each of the digits would be separately energized by signalsapplied from timing control circuit 11 through drive circuit 13'.

It is noted that the segment code signals and the digit code signalsapplied from divider to timing control circuit 11 may be of 2,048 Hz and256 Hz respectively. The segment signals and digit signals produced bytiming control circuit 1 1 are shown in FIGS. 4a and 4b respectively.Since there are seven segment electrodes in each digit and six digits,there are 42 separate elements that can be energized. If a duty cycle isselected to be less than l/42, each segment of the digit display can beindependently and sequentially lit. In this manner, only one segment isenergized at any instant, so that the energy required to drive thedisplay is /3 to A that consumed by a conventional digital displaywherein all of the digits are simultaneously energized. Moreover, thefrequency at which a display is energized is greater than or equal to 32Hz, the after-image effect of the human eye eliminates the flicker inthe display. In this manner, low temperature operation with a continuousdisplay can be achieved in a satisfactory manner.

In a third embodiment of the arrangement in accordance with theinvention, advantage is taken of the fact that the viewer cannotefficiently view the six digits of a time display simultaneously. In thethird embodiment, both hour digits, both minute digits and both seconddigits are sequentially displayed in turn, two by two. As moreparticularly shown in FIG. 5, the gate signals for driving both hourdigits is represented by waveform c, the gate signals for driving bothminute digits is represented by waveform d, and the gate signals fordriving both second digits are represented by waveform e. If the delaytime t is set at l/16 second or more, a distinct and readable timedisplay is provided wherein the hours, minutes and seconds aresequentially displayed. Further savings and energy consumption can beachieved by combining the instant embodiment with the embodiment ofFIGS. 1 and 3 respectively.

Various embodiments of the invention in accordance with the inventionutilize the after-image effect of the human eye, as well as the highlight-producing efficiency in relation to current characteristic oflight emitting diodes to provide an electronic timepiece having lowerpower consumption and an enhanced display. The watch construction inaccordance with the invention can be simply constructed through the useof integrated circuitry techniques.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above construction, it isintended that all matter contained in the above description or shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

What is claimed is:

I. In an electronic timepiece having oscillator means for producing highfrequency timekeeping signals; multi-state divider circuit means forproducing a low frequency timing signals from said high frequencytimekeeping signal, and digital display means for the digital display oftime in response to said timing signals, said digital display meansincluding at least two digits of time each digit of time being definedby a plurality of segments, the selective energization of certainsegments effecting the display of numerals from 0 to 9, the improvementwhich comprises timing control circuit means operatively coupled to eachof said segments of said digital display means to sequentially andrepetitively energize each segment of each digit of time, said timingcircuit control means being coupled to said divider means for receivingan intermediate frequency cycle control signal therefrom whereby eachsegment of each digit is actuated during a separate slot of each cycleof said timing control circuit means.

2. An electronic timepiece as recited in claim 1, wherein said digitaldisplay means includes digits for the display of at least hours andminutes, said timing control circuit means additionally sequentiallyactuating the hours digits as a unit and the minutes digits as a unit.

3. An electronic timepiece as recited in claim 1,

human eye.

1. In an electronic timepiece having oscillator means for producing highfrequency timekeeping signals; multi-state divider circuit means forproducing a low frequency timing signals from said high frequencytimekeeping signal, and digital display means for the digital display oftime in response to said timing signals, said digital display meansincluding at least two digits of time each digit of time being definedby a plurality of segments, the selective energization of certainsegments effecting the display of numerals from 0 to 9, the improvementwhich comprises timing control circuit means operatively coupled to eachof said segments of said digital display means to sequentially andrepetitively energize each segment of each digit of time, said timingcircuit control means being coupled to said divider means for receivingan intermediate frequency cycle control signal therefrom whereby eachsegment of each digit is actuated during a separate slot of each cycleof said timing control circuit means.
 2. An electronic timepiece asrecited in claim 1, wherein said digital display means includes digitsfor the display of at least hours and minutes, said timing controlcircuit means additionally sequentially actuating the hours digits as aunit and the minutes digits as a unit.
 3. An electronic timepiece asrecited in claim 1, wherein said timing circuit control meanssequentially energizes each of the digits of time.
 4. An electronictimepiece as recited in claim 3, wherein the duty cycle for thesequential energization of each of the segments and digits of thedigital display means is such as to render said digits simultaneouslyvisible to the human eye.
 5. An electronic timepiece as recited in claim1, wherein the duty cycle of the timing control circuit means for thesequential driving of all of said segments is such as to render samesimultaneously visible to the human eye.